Investments and Fair Value of Financial Instruments - Marketable Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	$ 13,960	$ 7,875
Less than 12 months: Gross Unrealized Losses	(4)	(3)
12 Months of more: Fair Value	0	0
12 months or more: Gross Unrealized Losses	0	0
Total: Fair Value	13,960	7,875
Total: Gross Unrealized Losses	(4)	(3)
U.S. states and municipalities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	1,408
Less than 12 months: Gross Unrealized Losses	(1)
12 Months of more: Fair Value	0
12 months or more: Gross Unrealized Losses	0
Total: Fair Value	1,408
Total: Gross Unrealized Losses	(1)
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months: Fair Value	12,552	7,875
Less than 12 months: Gross Unrealized Losses	(3)	(3)
12 Months of more: Fair Value	0	0
12 months or more: Gross Unrealized Losses	0	0
Total: Fair Value	12,552	7,875
Total: Gross Unrealized Losses	$ (3)	$ (3)